Someone visits their doctor or a hospital emergency room suffering from the symptoms of E. coli sickness, which include severe stomach cramps, watery or bloody diarrhea, vomiting and low-grade fever.

That single visit sets in motion a chain of events — a mix of high-tech science and old-fashioned detective work — that leads public health officials to link 16 cases of E. coli sickness from British Columbia to Newfoundland to the XL Foods Inc. slaughterhouse at the centre of the largest recall of meat in Canadian history.

“It is a bit like CSI in a lot of ways,” said Dr. Keith Warriner, director of the food quality assurance program at the University of Guelph.

The hospital laboratory will analyze a stool sample. If it finds E. coli O157:H7, which can be easily separated from the harmless strains of the bacteria in the intestines, it will send it off to the provincial laboratory for further testing.

There, scientists narrow down the strain through process called pulsed-field gel electrophoresis, which separates it into large chunks of DNA.

The resulting fingerprint — called a pulsed-field type — is shared electronically through PulseNet Canada, a national surveillance network that links the computers and databases of provincial and some federal laboratories so they can track the DNA fingerprints of most cases of salmonella poisoning and all cases of E. coli sickness.

Dr. Frank Plummer, chief science officer at the Public Health Agency of Canada, said the problem is that while the pulsed-field type of the strain of E. coli O157:H7 found at XL Foods is not “extremely common,” it is seen often enough that it would be difficult to say with confidence that someone who became ill from bacteria with the same pulsed-field type got it from eating beef produced there.

So, the strain would be sent to the National Microbiology Laboratory in Winnipeg for another level of testing called multilocus variant analysis (MLVA) to help narrow things down even more.

Plummer said the pulsed-field type and MLVA signature for the strain of E. coli O157:H7 found in beef products from XL Foods had never before been seen in Canada or the United States, so a match meant a link from one to the other.

“We are pretty confident that any cases we find in humans are linked to the XL plant,” Plummer said.

Much of this work was being done behind the scenes, as the role of the Public Health Agency of Canada received far less attention than the federal agriculture minister and the food inspection agency, both in the hot seat this fall as they fielding tough questions about their response to the E. coli scare at the XL Foods facility in Brooks, Alta.

That stood in contrast to three years ago, when Chief Public Health Officer Dr. David Butler-Jones — an unflappable character wearing a leather jacket and a Mickey Mouse watch — held almost daily news conferences about the H1N1 pandemic in 2009.

The top doctor is recovering from a mild stroke, but a government official said Butler-Jones would have come to the forefront if the public health agency had difficulty locating the source of the contamination, the illness was more widespread, more severe or people had died.

Health Canada spokesman Alastair Sinclair said Butler-Jones hopes to be back at work by late December or early January.

Liberal MP Carolyn Bennett (St. Paul’s) said the public health agency — created after the 2003 SARS outbreak in order to separate public health decisions and communications from politics — should have been the one reassuring Canadians about E. coli.

“No one is looking down the camera at people, telling them their beef is safe, except for politicians,” said Bennett, referring to the role that Agriculture Minister Gerry Ritz played in news conferences about the issue.

But Plummer dismissed the suggestion that Canadians were clamouring for a stronger presence from him and his colleagues.

“The main concern of Canadians, at least the press, has been about the food safety issue and not so much about the human cases,” Plummer said in an interview this week.

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